A human nose has various defense mechanisms to prevent impurities from entering the body. A screen of hairs is present at the entrance to the nose, which traps dust particles, tiny insects and other particles. Further, the nose has a nasal cavity lined with a mucus membrane that helps to warm excessively cool air and also blocks very fine dust particles that pass through the hair screen. However, mucus may accumulate in the nasal cavity and block the same thereby leading to respiratory infections.